Delphi FDMemtable中如何在已有的字段数据集上加入字段-木庄网络博客

本文整理自网络，侵删。
 //在原有数据集上是加不进去的。可以再做一个FDMemtable，然后
 
    FDMemTable_新数据集.FieldDefs.Assign(DataSet_原数据集.FieldDefs);
    FDMemTable_新数据集.FieldDefs.Add('新加字段', ftFloat);
    FDMemTable_新数据集.CreateDataSet; //建立数据集
 
    //将数据转移过来  
    FDMemTable_新数据集.CopyDataSet(DataSet_原数据集[coAppend]);
   //
 
    while not FDMemTable_新数据集.eof do
    begin
      FDMemTable_新数据集.edit;
      //给新字段赋值 或者用计算字段显示赋值。
      FDMemTable_新数据集.Post;
      FDMemTable_新数据集.next;
    end;
其他人写的代码：
procedure TForm1.AddFieldTest;
var
  DataFN : String;
  TempMemTable : TFDMemTable;
begin
  // Added, to avoid relative path for data file name
  DataFN := ExtractFilePath(Application.ExeName) + 'Data.Xml';
 
  FDMemTable1.FieldDefs.Add('ID', ftInteger, 0, false);
  FDMemTable1.FieldDefs.Add('name', ftString, 30, false);
  FDMemTable1.FieldDefs.Add('QualityID', ftInteger, 0, false);
 
  FDMemTable1.CreateDataSet;
 
  // i fill the the table with some value
  FDMemTable1.Open;
  FDMemTable1.AppendRecord([1, 'Movie1', 1]);
  FDMemTable1.AppendRecord([2, 'Movie2', 2]);
  FDMemTable1.AppendRecord([3, 'Movie3', 1]);
 
  // after seeing the value on the grid, i push a button and save the table as XML
  FDMemTable1.saveToFile(DataFN);
 
  // Added, close the dataset and clear the FieldDefs
  // Without the FieldDefs.Clear call, your code produces a "Duplicate field ID" error 
  FDMemTable1.Close;
  FDMemTable1.FieldDefs.Clear;
 
  // now after closing the program and running it again, i want to load the data with a new FieldDef Called Episode with a default value 0
  // the table is connected to cxGrid, and the moment i try to load, i get the error i mentioned.
 
  FDMemTable1.FieldDefs.Add('ID', ftInteger, 0, false);
  FDMemTable1.FieldDefs.Add('name', ftString, 30, false);
  // this line is NEW
  FDMemTable1.FieldDefs.Add('Episode', ftInteger, 0, false);
  FDMemTable1.FieldDefs.Add('QualityID', ftInteger, 0, false);
 
  FDMemTable1.CreateDataSet;
 
  // check the FieldCount and existence of the Episode field
  Caption := IntToStr(FDMemTable1.FieldCount);
  Assert(FDMemTable1.FindField('Episode') <> Nil);
 
  //  Create a temporary TFDMemTable
  TempMemTable := TFDMemTable.Create(Nil);
  try
    //  load the data into the temporary TFDMemTable
    TempMemTable.loadFromFile(DataFN);
    //  copy the data from the temporary TFDMemTable into FDMemTable1
    FDMemTable1.CopyDataSet(TempMemTable, [coAppend]);
 
  // check the FieldCount and existence of the Episode field
    Caption := IntToStr(FDMemTable1.FieldCount);
    Assert(FDMemTable1.FindField('Episode') <> Nil);
  finally
    TempMemTable.Free;
  end;
end;

来源：https://blog.csdn.net/lyf_lyf/article/details/98631026
Delphi FDMemtable中如何在已有的字段数据集上加入字段

相关推荐

评论
